Table 2. Timing of patent filing and issue relative to drug approval, by category.

	Number (share) filed post approval	Number (share) issued post approval
Chemical compound patents (n = 364)	6 (2%)	40 (11%)
Independent formulation patents (n = 430)	91 (21%)	201 (47%)
Independent PIPES patents (n = 143)	34 (24%)	67 (47%)
Independent method of use patents (n = 579)	130 (23%)	261 (45%)

Legend: Based on the patents associated with the 432 new molecular entities (with at least one patent) approved by the U.S. Food and Drug Administration between 1985 and 2005. Categories are based on authors' coding of the claims in these patents. “PIPES” refers to Polymorph, Isomer, Prodrug, Ester, and Salt claims. “Independent” secondary patents in a category are those with no chemical compound claims.